Chemistry / by George Wilson.

  • George Wilson
Date:
1857
Catalogue details

Licence: Public Domain Mark

Credit: Chemistry / by George Wilson. Source: Wellcome Collection.

    94/348 page 86
    pression and reduction of temperature may lie simultaneously had recourse to, which is the process generally followed for the condensation of gases. 306. A liquefied gas is always a very volatile body, and may often be in part solidified or frozen by permitting the liquid to evaporate spontaneously. Thus liquid carbonic acid, if allowed to evaporate rapidly, acts exactly like water con- fined in the air-pump vacuum along with oil of vitriol. One portion of the liquid becomes gas, the other changes into solid carbonic acid, a substance scarcely distinguishable in external characters from snow. 307. Some gases do not require this process, but, by mere reduction in temperature, may be frozen like water. In short, the great majority of the gases comport themselves exactly as the vapours evolved by liquids do—the difference between them being’ only one of degree, so that a greater amount of cold is required to condense the gas than to condense the vapour. This, however, implies no greater difference between a gas and a vapour than between two vapours, no one of which contains the same amount of latent heat as another, or requires the same reduction of temperature to render it liquid. 308. Some gases, such as oxygen, nitrogen, and hydrogen, have as yet resisted every attempt to liquefy them; but we do not doubt that this is only because they are the vapours of bodies so highly volatile, that we are not able to command a temperature low enough, or a pressure sufficient to induce them to part with their latent heat.
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